A liquid crystal display system of this type comprises a liquid crystal display panel, a driving circuit, and peripheral devices such as backlight. FIG. 13 represents schematical cross-sectional views to explain an approximate arrangement example of a typical longitudinal electric field type (the so-called TN type) liquid crystal display system. Normally, in a liquid crystal display panel, which constitutes an active matrix type liquid crystal display system, a liquid crystal LC is sealed between a first panel PNL1, which is composed of a first substrate (an active matrix substrate or a thin-film transistor substrate; TFT substrate) and a second panel PNL2, which is composed of a second substrate (a counter substrate or a color filter substrate; CF substrate).
On an inner surface of a first substrate SUB1, which constitutes a first panel PNL1, there are provided a thin-film transistor TFT and a pixel electrode PX driven by the thin-film transistor TFT. On the uppermost layer, a first orientation film ORI1 is deposited, and an ability to control liquid crystal orientation is provided. Also, on an outer surface (back surface), a first polarizing plate POLL is attached. On the other hand, on an inner surface of a second substrate to constitute a second panel PNL2, there are provided a color filter CF, a light-shielding layer (black matrix) BM to partition off between color filters of adjacent pixels, and a counter electrode CT. On the uppermost layer, a second orientation film ORI2 is deposited, and an ability to control liquid crystal orientation is provided. Also, on an outer surface (front surface), a second polarizing plate POL2 is attached, which has a polarizing axis perpendicularly crossing the polarizing axis of the first polarizing plate POL1. In the figures, detailed arrangement is not shown.
In the manufacturing process to fabricate the thin-film transistor TFT on the first substrate SUB1, a plurality of gate lines and gate electrodes extending from the gate lines made of metal film such as chromium, are arranged for each pixel in parallel to each other. In general, the width of the gate electrode is narrower than the width of the gate line. Then, an insulating layer, an active layer, (silicon semiconductor layer), data lines, data electrodes (source and drain electrodes), pixel electrodes, protective films, orientation films, etc. are formed. By giving an ability to control liquid crystal orientation to the orientation film, the first substrate is prepared. On a back surface of the first substrate SUB1, a backlight BLK is mounted. The circuit to drive this liquid crystal display panel is not shown in the figure.
FIG. 14 represents schematical drawings to explain an arrangement of one pixel of the liquid crystal display panel explained in connection with FIG. 12 and an arrangement of a thin-film transistor to constitute this pixel. Specifically, FIG. 14 (a) is a plan view of the pixel, and FIG. 14 (b) is a cross-sectional view along the line A-A′ in FIG. 14 (a). As shown in FIG. 14 (a), the thin-film transistor TFT is disposed at an intersection of the gate line GL and the data line DL. Also, a pixel electrode PX to constitute a pixel is connected to a source electrode (or a drain electrode) SD1 of the thin-film transistor TFT via a contact hole TH, and an auxiliary capacity is formed between an auxiliary capacity line CL and the pixel electrode.
In FIG. 14 (b), a gate electrode GT extending from the gate line GL and a gate insulator film GI to cover the gate electrode GT are formed on an underlying film UW prepared on the surface of the first substrate SUB1 in the thin-film transistor TFT. On this gate insulator film GI, a silicon (Si) semiconductor layer SI as an active layer and an ohmic contact layer (n+Si) NS, a source electrode SD1 and a drain electrode SD2 are laminated sequentially. The underlying film UW is made of a laminated film comprising silicon nitride and silicon oxide.
To cover the gate line GL and the gate electrode GT, a gate insulator film GI preferably made of silicon nitride (SiNx) is deposited, and a plurality of data lines DLs to cross the gate lines GLs are formed. At the same time as the formation of the data lines DLs, a source electrode (or a drain electrode) SD1 and a drain electrode (or a source electrode) SD2 are prepared in the same layer.
In case of full-color display, the pixel is a sub-pixel of each single color (red, green, or blue). Here, it is simply called “pixel”. As described above, the thin-film transistor TFT to constitute the pixel comprises a gate electrode GT, a silicon semiconductor film SI prepared by patterning on the gate electrode, an ohmic contact layer (n+ silicon) NS separately formed on upper layer of the silicon semiconductor film, and a source electrode (or a drain electrode) and a drain electrode (or a source electrode) connected respectively to the separated ohmic contact layers.
On upper layer of the thin-film transistor, a protective film PAS is deposited. On it, a pixel electrode PX preferably made of ITO is prepared by patterning and is connected to the source electrode (or the drain electrode) SD1 via a contact hole TH formed on the protective film PAS. A first orientation film (see FIG. 13) is prepared to cover the pixel electrode PX.
On the other hand, on another substrate not shown in the figure, a counter electrode is formed via color filters for three colors in case of full-color and a smooth layer (overcoating layer) (not shown in FIG. 13). A second orientation film (see FIG. 13) is deposited to cover the counter electrode, and this is superimposed on the active matrix substrate, which is another substrate as described above, and a liquid crystal is sealed in a gap between them.
The preparation of lines or the like of the active matrix type substrate by using the ink jet method as described above is disclosed in the Patent Document 1. In the Patent Document 1, it is described that the gate electrode of the thin-film transistor TFT is prepared by ink jet method using a liquid material containing an electroconductive material, and the source electrode and the drain electrode of the thin-film transistor TFT are prepared by the ink jet method using a liquid material containing a semiconductor material. The Patent Document 3 is an example of references to disclose mask-less exposure to light as described later.
[Patent Document 1] JP-A-2003-318193
[Patent Document 2] JP-A-2000-249821
[Patent Document 3] JP-A-2002-520840